Never before have highly capable drones been so inexpensive and widely available.

But with this new frontier comes problems, and how we proceed in terms of regulation will dictate whether the drone industry can take off in the United States.

Perhaps a perfect example of the problems that can arise came last August when nearly 100,000 football fans gathered at Darrell K Royal-Texas Memorial Stadium in Austin to watch the Longhorn football season opener.

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Hovering above the stadium was a drone with blue and red blinking lights.

The police watched as the drone shifted from one area of the stadium to another.

When the drone’s operator finally recalled the device and landed it at his feet in a nearby parking lot, the police immediately took both drone and operator into custody.

The situation turned out to be no more menacing than a devoted, but ticketless, football fan trying to watch the game through the video feed on his drone.

But the police could not have known this beforehand and had to treat the incident as a potential chemical, biological or explosive attack on the multitude of gathered spectators.

As we enter an age of highly capable and increasingly autonomous drones available for purchase for a few hundred dollars over the Internet, the intrusion at the football stadium will be replayed in various forms at sites all over the United States, some crucial to security.

The great majority of these incidents will be accidental, such as the flyaway drone that recently crashed on the White House grounds.

But in the early stages of a UAV incursion, it will be impossible to distinguish the accidental from the intentional, the benign from the malicious.

The distressing truth is that even consumer-grade drones can be rigged to carry out potent attacks against which our defenses will either be only weakly effective or so militarized that the defenses themselves will pose a threat to the surrounding civil infrastructure.

So what should the Federal Aviation Administration do? Let’s start with what they should not do.

Imposing restrictions on small UAVs beyond the sensible restrictions the FAA recently proposed would not significantly reduce the threat of rogue drones or their operators.

But additional restrictions would shackle the emerging commercial drone industry.

Even the FAA’s current ban on non-line-of-sight drone control would be of little consequence to a criminal capable of modifying open-source autopilot software.

The best way forward is for the FAA to adopt simple measures that sharply reduce the risk of accidental or unsophisticated drone incursions, such as voluntary manufacturer-imposed geofencing.

For high-security sites such as the White House, detection and tracking systems based on electro-optical sensors will be most effective, particularly those applying infrared sensor pattern recognition to distinguish a drone’s warm motors and batteries from a bird’s warm body.

A squadron of at-the-ready interceptor drones, guided by the tracking system, could snare the intruder in a net and haul it off.

Cities such as Paris, where drones seem to pop up regularly around nuclear plants and government buildings, could adopt a large-scale version of this system, deploying electro-optical sensors and interceptor drones at key sites across the city.

We should refrain from any more drastic measures than these until the threat of drones proves to be more of a menace than recent incidents, which were alarming but nonetheless harmless.

Todd Humphreys is an assistant professor of aerospace engineering and engineering mechanics in the Cockrell School of Engineering at The University of Texas at Austin.